The PC at 20 - An Upgrader's Perspective

The PC at 20 - An Upgrader's Perspective

20 years ago, on August 12, 1981, IBM's Personal Systems division
in Boca Raton, Florida rolled out the IBM Personal Computer Model 5150, a system
better known as the original IBM PC.

While it wasn't the first "personal computer" (many
credit the 1975 MITS Altair as the first), it was the first "PC",
where PC means a class of personal computers that are compatible with each other.
Today, PCs account for approximately 95% of the personal computer market.

The original IBM PC's modular, expandable design spawned a
whole industry of compatible hardware and software to follow, making PCs the
defacto standard personal computers used by most people around the world. The
systems we call "PCs" today are really just compatible evolutionary
descendants of the original IBM PC system. It is a testament to the standardization
of the PC that amazingly almost all of the operating systems and software (and
much of the hardware) designed for the first IBM PCs in 1981 still function
on a modern PC today!

On the 20th anniversary of this computing revolution, it's
useful to see how the design of the IBM PC not only established a new dominant
species among personal computers, but also made upgrading and inexpensive repairing
possible, and how it continues to affect our upgrade and repair possibilities
today.

Open Architecture - Then

The IBM PC broke with other personal-computing pioneers by
providing an open, expandable architecture. Rather than insisting upon making
sure that every component inside the IBM PC was a custom component created internally,
IBM, unlike the competition, made extensive use of off-the-shelf components.
Starting with the motherboard, the main processor and virtually all of the supporting
chips came from Intel. Because IBM was nervous about having a single supplier
for these components, they required that Intel license the chips to other companies,
such as AMD, NEC and Harris. So, for example, a disaster at an Intel chip plant
wouldn't put IBM out of the PC business. IBM's forcing their major suppliers
to license their technology was one of the central reasons that made the PC
what it is today, and helped to foster competition among the suppliers that
has kept options open and prices down to this day. AMD got their start in the
PC processor business because Intel licensed them to make exact copies of the
early Intel processors, all thanks to IBM.

For disk interfaces IBM sought pre-existing standards rather
than develop custom solutions such as those that Apple had been known for. The
floppy disk drives used the standard Shugart SA-400 interface and came from
companies like Shugart, Tandon, and Control Data. Hard drives used the standard
Seagate ST-506/412 interface and came from companies like Seagate, MiniScribe,
and IMI.

This use of standard interfaces and components carried on to
peripherals as well. The PC was available with industry standard RS-232 serial
interfaces as well as the parallel printer interface that Centronics self-named
and developed. The first IBM printers were actually modified Epson dot-matrix
printers

IBM published detailed documentation and schematic circuit
diagrams for their systems, and even included full source code listings of their
BIOS, which allowed developers to create add-in boards. Soon multi-function
cards from companies like Quadram and AST began to replace the inefficient one-function,
one-card design of a stock IBM PC, which had only a single slot to perform all
types of I/O.

Open Architecture - Now

The interior of a PC today is different in detail than on the
early IBM PCs. PCI and AGP slots have replaced 8/16-bit ISA slots, motherboard
and power supply form factors have changed, and drives are much smaller in form
factor, while also much larger in capacity. Despite all that, the open-architecture
philosophy still reigns supreme.

Attempts to put a proprietary flair on the PC architecture,
such as the IBM MicroChannel bus equipped PS/2s of the late 1980's and early
1990's have flopped, and deservedly so. The same holds true for the LPX-based
systems produced by companies such as Packard-Bell. Today's systems are largely
based on industry-standard form factors like ATX, Micro-ATX and NLX. So, just
as in the pioneering PC days, you can replace practically everything from the
power supply to the motherboard and improve your system dramatically in the
process. And, thanks to IBM's demand on Intel and others to provide alternative
sources for their components, companies like AMD began to develop the expertise
that has led to the highly competitive Athlon and Duron processors.

BIOS Limitations - Then

It wasn't long before the first PCs required upgrades to the
BIOS to either correct bugs or add new features. While it took more than a decade
to develop the field-upgradable flash memory BIOS chips common today, periodic
BIOS chip upgrades for PC, PC-XT, AT, and clone/compatible systems became an
occasional annoyance for many users during the 1980's and early '90's. These
upgrades required opening the system, as well as the removal and replacement
of the socketed BIOS chip.

BIOS Limitations - Today

The pace of technology change has accelerated, as have the
need for BIOS upgrades. Fortunately, it's increasingly rare to need to physically
replace the BIOS chip on today's systems, but many users will perform at least
one downloadable BIOS upgrade during the life of their systems. While the packaging
and location of the BIOS chip has changed, the ability to upgrade the firmware
that enables the system to cope with newer devices and software is another legacy
of the IBM PC.

The open architecture of the IBM PC, and the division of management
tasks between the BIOS and the operating system also made it possible for 3rd-party
BIOS vendors like Phoenix, Award (now part of Phoenix), and AMI to engineer
work-alike BIOSes with more features. These BIOSes are found inside the vast
majority of new systems today, even those from major vendors such as Gateway,
Dell, MicronPC and others.

Power and Drive Upgrades - Then

The original 5-slot IBM PC had a physically huge but appallingly
underpowered 63.5-watt power supply. The 8-slot, hard-drive version (the IBM
PC/XT) had a less-underpowered 130-watt power supply. Thanks to open architecture,
it didn't take long for third-party vendors to build better, more powerful power
supplies to replace the original units, providing the power needed for cards
in every slot and drives in every bay.

Similarly, the IBM PC's original 160/180KB single-sided floppy
drives were quickly replaced by double-sided 320/360KB models, and the original
10MB hard disks by larger 20MB, 30MB, and even 40MB models. The IBM PC and PC/XT's
motherboard had no built-in I/O controllers except for a keyboard, everything
from the floppy controller to the hard disk controller, as well as serial/parallel
and even mouse ports all had to be added via plug-in cards. The original PC
and XT didn't even have a clock, and there was no CMOS RAM either, the system
configuration was entirely controlled by dip switches on the board. Several
vendors sold clock cards (often combined as part of a multifunction card) which
included their own software to set the date and time in the operating system.

The original IBM PC and PC/XT provided users with a choice
between tack-sharp green text (but no graphics) or "colorful" 4-color
CGA graphics and fuzzy text. Even in the early days of the PC, 3rd-party vendors
like Hercules put sharp text and graphics together for green-screen users, and
IBM eventually developed better video standards such as EGA and today's baseline,
VGA.

Power and Drive Upgrades - Today

Today's PC vendors, with few exceptions, are still up to their
old tricks when it comes to power supplies, drives, and video: installing the
smallest and cheapest components that get the systems out the door.

Fortunately, bigger, faster, better replacements for power
supplies, drives, and video cards are just a purchase and a screwdriver away.
Again, while the details of the PC have changed over time, the open architecture
of the PC standard that IBM created has continued into today's models, giving
you the ability to change anything you like.

Operating Systems = Then

When their first PC was being developed in 1980-81, IBM had
a choice between the established (Digital Research's CP/M) or something entirely.
IBM chose Microsoft, then famous primarily for its version of BASIC, to provide
an operating system. Microsoft licensed Seattle Computer Products' "quick-and-dirty"
operating system (which looked and felt a lot like CP/M) and turned it into
MS-DOS. IBM called their version PC-DOS, but didn't prevent Microsoft from selling
it to other computer vendors under the MS-DOS name.

Operating Systems - Today

Love Microsoft or hate it, if IBM had prevented Microsoft from
selling MS-DOS to other vendors, the PC business today would be as closed today
as the Apple Macintosh systems are. There wouldn't be the choice in system manufacturers,
components, and even software that we have today. Had IBM not allowed Microsoft
to license, and had Apple seen the light and licenced their system, we would
all be using their systems today. The de facto standard status of PC-DOS/MS-DOS
helped provide a common basis for software, even as IBM, along with Intel processors
and chipsets provided a common hardware basis.

While Microsoft Windows has become, in the eyes of some, a
dangerous monopoly, the open architecture and common standards of the PC world
is making it easier for potential rivals such as Linux to have a chance at nibbling
away at Microsoft's dominance. Administrators of Linux-based Apache web servers,
for example, haven't had to worry about the proliferation of attacks such as
RedWorm and RedWorm 2 against the Internet, since Microsoft's servers are much
more vulnerable.

Conclusion

While increasingly low-cost PCs integrate sound, video, and
even modem and network functions into the motherboard, and reduce slot count,
the open architecture design that the IBM PC inspired continues to make upgrading
possible and desirable. From the least expensive "home" computer to
a fire-breathing gamer's dream, any PC user can still replace everything from
the keyboard to the motherboard and get a better system, a task that simply
can't be done to the same extent with Apple or any other hardware platform.
Thank you, IBM, for creating an open architecture PC!